It is a standard procedure when joining two metallic bodies to weld them together by the standard fusion-welding technique where the juxtaposed metallic workpieces are heated at their interface until one or both of them actually melts and bonds with the other workpiece. The resultant joint is extremely strong and works well even when, for instance one tube end is swaged out so it can fit over another tube end for fusion-welding thereto, although it normally somewhat reduces the thickness and strength of both the workpieces at the joint.
When however joining very thin workpieces less than 1 mm thick such a procedure leads often to an excessive weakening of the already thin material. The cause of this is the liquefied material of one of the workpieces that has been displaced to join with the other workpiece and the heating which can cause a metal to lose strength. The joint region is normally where stresses from vibration are most apparent, so this critical region is going to be weaker than the rest of the structure. Thus such construction normally leads to failure of the joint regions while the rest of the structure still has considerable service life left.